Disk properties and density structure of the star-forming dense core B335

We present subarcsecond-resolution dust continuum observations of the protostellar collapse candidate B335 made with the IRAM Plateau de Bure Interferometer at wavelengths of 1.2 and 3.0 mm. These observations probe to less than 100 AU size scales and reveal a compact source component that we identify with a circumstellar disk. We analyze these data in concert with previous lower resolution interferometer observations and find a best-fit density structure for B335 that consists of a power-law envelope with index p=1.55+/-0.04 (rless than or similar to5000 AU) together with a disk (r<100 AU) of flux F(1.2mm)=21 +/- 2 mJy. We estimate a systematic uncertainty in the power-law index delta p less than or similar to 0.15, where the largest error comes from the assumed form of the dust temperature falloff with radius. This determination of the inner density structure of B335 has a precision unique among protostellar cores, and it is consistent with the r(-1.5) profile of gravitational free fall, in accord with basic expectations for the formation of a star. The flux (and implied mass) of the compact component in B335 is typical of the disks around T Tauri stars.